The present invention relates to the field of functional devices for the disabled and, in particular, but not exclusively, to a system for the control and monitoring of functional upper-limb prostheses with energy from outside the body. The present invention also relates to a method for the remote control of a system of this type.
In recent years, progress in electronics has also given a technological boost to the field of devices for the disabled. Reference is made in particular to biotechnological devices, to carriages, and to prostheses with a high technological content, in which the presence of sensors and of electronic components improves the performance of the device.
The upper-limb prosthesis is certainly one of the functional devices for the disabled which presents the greatest technological problems in its construction and control. In particular, the provision of a prosthetic hand is particularly difficult because of aspects connected both with aesthetics and with functionality, as; well as with the actual degree of complexity of this member.
A human being""s upper limb is used not only for its gripping capability, but often as a means of indirect or direct communication, for example, in people who suffer from a speech defect, or for assessing the nature, consistency and physical characteristics of an object by means of sensory receptors of various kinds,
Owing to this complexity, there are many known solutions for upper-limb prostheses which differ from one another according to their functional characteristics and to the type of energy used for their operation. In particular, it is possible to distinguish between passive prostheses, amongst which are cosmetic, operative, exoskeletal or endoskeletal prostheses, and active prostheses, amongst which are those using body energy, those using energy from outside the body, and those with myoelectrical or electronic control.
An active upper-limb prosthesis with energy from outside the body uses energy supplied by a storage device to drive one or more direct-current electric motors the movement of which brings about closure or opening of an artificial hand, flexion-extension of an artificial elbow, and pronation-supination of an artificial wrist of the prosthesis. These prostheses are divided further into myoelectrical and electronic prostheses according to the type of control source used, that is, according to the type of sensor.
Myoelectrically-controlled prostheses use as sensors surface electrodes which are placed in contact with the skin of the natural limb and can detect an electromyographic signal generated as a result of an isometric contraction of the underlying muscles. This signal, which arises from the intrinsic contraction mechanism of the muscle fibre, has a very low value such that it has to be reprocessed to produce a significant signal for the control circuits of the prosthesis. A necessary condition in order to be able to use signals of this type is that they must have an amplitude such as to be recognized by the sensor and that they must be capable of being generated independently of one another.
In the field of functional devices for the disabled, developments in mechanical and electronic technology have led to the use of ever more sophisticated and complex technological components in order to achieve results as similar as possible to those of a natural limb. This increase in complexity has created the need for ever more rapid and precise management of the control parameters of the prosthetic devices, making it necessary to back them up with microprocessor circuits.
Another problem resulting from these recent developments is connected with pre-setting, calibration, and resolution of breakdowns in devices of this type, requiring skilled personnel and specialized equipment which are often difficult to find in the field.
The object of the present invention is to provide a system for the control, monitoring and management of functional devices for the disabled with energy from outside the body and, in particular, of upper-limb prostheses, which solves the above-mentioned problems.
Another object is to provide a method for the remote control and management of devices of this type, both for periodic maintenance and in the event of unexpected breakdown or malfunction.
A further object of the present invention is to provide a functional device for the disabled which is safe and reliable, which can be maintained quickly, and which can easily be adapted to the specific requirements of each individual patient.
To achieve the objects indicated above, the subject of the invention is a system for the control and monitoring of functional devices for the disabled with energy from outside the body, and a method for the remote control thereof, as defined in the appended claims.
In a particular embodiment of the present invention, a functional device for the disabled comprises a microprocessor electronic-control element which acquires surface electrical potentials generated by the contraction of the muscles, using them, after a processing stage, as signals for the control of the prosthesis, and controlling a plurality of drive means, for example, but not exclusively, direct-current motors.
One of the main advantages of the present invention is that the number of signals input to the control element can be minimized, when required, without thereby reducing the capabilities and the management characteristics.
Another advantage of the present invention consists of the use of skin electrodes for detecting surface electrical potentials, since they can be fitted on the patient without surgical operations, and maintenance operations can be minimized. Moreover, the technical characteristics of these electrodes enable a slowly variable and rectified signal to be produced, which can easily be converted into a digital quantity.
In one embodiment of the present invention, the signals are processed by a micro control unit (an MCU) which can detect the stimuli, operate the motors, and check that the circuits and the motors are not subject to operating parameters greater than their specifications. The MCU recognizes three families of signals: that of signals which are generated by the patient""s muscles and are devoted to bringing about a movement, that of muscle signals which are devoted to selecting the function to be selected, and that of signals which are generated by the motors or by the sensors and are devoted to protecting the prosthesis.
The use of a processor (an MCU) also enables the principle functions performed by the functional device for the disabled to be implemented by means of programming codes so that it is not necessary to operate on electronic circuits and there is no need to design an individual electronic circuit for each different function. The adoption of these characteristics is also particularly advantageous in terms of saving of time at the stages of the production of prototypes and the pre-setting and calibration of the device.
A further advantage of the present invention is that it allows for maximum adaptability of the control element to very varied patients"" needs by the definition of a set of operative parameters at the fitting and training stage so as to render the use of the functional device as direct and natural as possible.
In a particular embodiment of the present invention, an 8-bit MCU with integrated peripherals has been selected so as to minimize size and the consumption of energy by the control system for given functions implemented.
Another important characteristic of the present invention is the adoption of a motor brake element, for example, but not exclusively, an electronic brake element, for keeping the various drive means in position in the absence of stimuli from the skin electrodes. When a patient provided with an electromechanical elbow is carrying a load or sets the position of any portion of the functional device, the position is thus maintained, even after external stresses, without the system having to make an active compensation effort.
In order to maintain a high degree of safety and reliability, the functional device of the present invention also comprises means for preventing excessive electrical stresses on the drive means and on the electronic circuitry. For example, but not exclusively, the MCU comprises an ADC port which constantly monitors current consumption by means of a particular integrated circuit, converting the measurement of current absorbed by the supply to a proportional voltage level. When the voltage exceeds normal operating levels for a period of time greater than a predetermined period, the processor stops the drive means and waits for the patient""s muscles to relax. One embodiment of the present invention also comprises means for detecting the travel limits of the various portions of the functional device so as to prevent wear or breakage of the mechanical and/or electronic components.